Perhaps the silliest debate underway in Israel these past weeks is over why Israelis are fleeing the country for the greener pastures of Europe and America.

The finance minister himself, Yair Lapid, has chided young Israelis for settling in the city Adolf Hitler once called home. "I'm a little impatient with people who are willing to throw the only country the Jews have into the trash can because Berlin is more convenient, he thundered from his Facebook page a month ago.

To his credit, Lapid framed his criticism as old-fashioned, moralistic Zionism. He didn't try to elaborate on why Israelis would be tasting from the fleshpots of Berlin. But an array of commentators rushed in to explain the distressing phenomenon of yerida – "descent" in Hebrew, meaning simply to leave Israel - as a function of political hopelessness in the absence of a peace process, the rigidities of the Israeli economy that prevent the best and brightest from achieving their potential and/or the impossibly high cost of living that puts any semblance of a middle class lifestyle far from reach for so many.

Yerida doesn't have quite the stigma it once had for a country that aspires to gather up the world's dispossessed Jews and give them a home. But it makes a useful tool for scoring ideological points.

"See, the government's policies are a disaster. People are fleeing the country because of whatever it is I disapprove of." That explains why -- just like the hoax research that erupted in the media a decade ago about blondes fated for extinction because the trait is carried in a recessive gene -- the yerida fact is too good to be checked.

Just the facts, ma'am

The greatest fact of them all is that emigration is hard to measure. Governments can collect data on people coming into or out of a country, but it's much harder to learn why they are doing it and what their long-term plans are.

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Who is a true yored? A Russian immigrant who goes back his country of origin after five years in Israel? Someone who spends a decade in Silicon Valley before coming back to Israel? How many of those 20,000 Israelis in Berlin plan to spend their lives there? If you asked them, many probably couldn't tell you.

Yinon Cohen, a Columbia University academic, sought to cut through this tangle of problems, drawing data from a variety of sources and taking a few educated guesses. He came up with a figure of 544,000 Israelis living abroad as of 2006.

Of those, 300,000 were foreign-born, many of them Russians who immigrated to Israel and then moved on. Technically speaking they may be yordim who let down the Zionist enterprise, but they hardly count as a black mark against Israel. Immigrants who return to their native countries are a fact of life – the rate for those coming to Britain in the decade to 2006 was 40% and in the United States the return rate is estimated at between 25% and 40%. In Israel, the Central Bureau of Statistics says that just 10% of the Russians who arrived in the 1990s wave of immigration subsequently emigrated.

Just one of the pack

Taking figures from a survey by the Organization for Economic Cooperation and Development and adjusting them for the fact that Israel has such a large immigrant population, Cohen concluded that Israel had an emigration rate of just under 6% of its population, putting it at the same level as countries like Canada and Finland, and not much higher than the OECD median.

Those figures come from the year 2000, but the fact is there's no reason to assume the emigration rate has grown. According to the statistics bureau, the number of Israelis leaving the country for a year or longer shot up in 2001 and 2002 to more than 27,000 annually as the Second Intifada was gathering storm, but it has pretty much fallen since then and was just 15,700 in 2011. The number of returning Israelis rose slightly over the period.

To those who would like to see a political statement in the figures, be warned that the rate of exits rose in the first years of the Oslo peace process. They rose again in the first years of the Second Intifada, too, but they quickly declined, long before the violence subsided.

Those who try to make social-justice hay out of yerida will also have a hard time trying to relate it to the numbers: Although the last decade, according to some economic observers, has been a period of growing distress for the middle class, the rate of Israelis leaving the country for a year or more declined. In any case, the vast majority of Israelis who leave head for the U.S., the home in unbridled capitalism and gaping income inequalities, rather than the social paradise of Europe. Indeed, the figures show that America draws the best-educated of all the Israeli immigrants.

And that leads to the one distressing factor in all the yerida figures, namely that the Israelis who do chose to get up and go tend to have the most skills and education.

Losing the X factor

The fact that two of the three Nobel prize winners this year in chemistry this year were Israelis who left for the U.S. is an embarrassing reminder of the extent to which local talent has fled. Dan Ben-David, the director of the Taub Center for Social Policy Studies, found that the percentage of Israeli academics working abroad is 10 times or more the rate for most other developed economy, with close to 29% of them overseas in 2007-2008.

Tens of thousands of Israelis are living in Silicon Valley, enough of them engineers and other tech professionals that they could easily fill the shortage of 8,000-10,000 the high-tech industry back at home suffers.

But these figures should be kept in context. The academic exodus says a lot about the under-investment in higher education over the last decade, a policy whose absurdity is hard to fathom in an economy so reliant on its human capital. The sizable Israeli expat community of California points an accusing finger at the failure of Startup Nation to deliver jobs even for engineers. But these are industry-specific policy problems for the government, not evidence that Mother Zion can't hold on to her children.

It is hard to gauge the true extent of yerida. Not everybody leaving has a plan to stay abroad, for instance.Adi Emanuel

Haaretz.com, the online edition of Haaretz Newspaper in Israel, and analysis from Israel and the Middle East. Haaretz.com provides extensive and in-depth coverage of Israel, the Jewish World and the Middle East, including defense, diplomacy, the Arab-Israeli conflict, the peace process, Israeli politics, Jerusalem affairs, international relations, Iran, Iraq, Syria, Lebanon, the Palestinian Authority, the West Bank and the Gaza Strip, the Israeli business world and Jewish life in Israel and the Diaspora.